Replace stopper for the Flexi dog leash.
Tested on Flexi New Coмfort tape L 8m 50kg.

If the leash stops locking when you press the button, it may be due to wear and tear on the stopper.
You need to print with 6-7 perimeters. It's better to use PA6-CF or something similar.

The part has been tested for several months in real conditions and works reliably

Note: the leash body is held together from the inside by metal ribbed pins around the perimeter. To open it, use a thin, wide screwdriver in one place to pry open and separate the halves of the body. Then, gradually move around the circumference.